Yarn guard for checking yarn travel in a textile machine



' Jan. 2, 1968 w. GITH 3,361,314

YARN GUARD FOR CHECKING YARN TRAVEL IN A TEXTILE MACHINE Filed July 14,- 1965 2 Sheets-Sheet 1 Jan.2,1968 Q\IN.GITH 3,361,314

YARN GUARD FOR CHECKING YARN TRAVEL IN A TEXTILE MACHINE Filed July 14, 1965 I 2 Sheets-Sheet 2 a A "gvtfliiw R? Q N @5 q; u 'VWWM M Q lhl FIG. 3c

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United States Patent YARN GUARD FQR CHECKING YARN TRAVEL IN A TEXTILE MACHINE Walter Gith, Monchen-Gladbach, Germany, assignor to Walter Reiners, Monclien-Gladbach, Germany Filed July 14, 1965, Ser. No. 471,880 Claims priority, application Germany, July 15, 1964, R 38,378 7 Claims. (Cl. 22611) ABSTRACT OF THE DISCLOSURE Yarn guard for checking yarn travel along a path in a textile machine has sensing means located adjacent the yarn travel path and adapted to oscillate mechanically in response to movement of the yarn past the sensing means and to cease oscillating in response to a break in the yarn, and transducing means connected with the sensing means for converting the mechanical oscillations thereof to electrical oscillations. The sensing means has a rod slidingly engageable by the traveling yarn and me chanically oscillatable thereby and the transducer has a piezoelectric crystalline plate. The rod extends substantially perpendicularly to the longitudinal axis of the crystalline plate and is either connected directly by an end thereof to a side of the plate or to one end of a substantially L-shaped support member secured by its other end to an end of the crystalline plate.

My invention relates to a yarn guard for checking yarn travel in a textile machine.

Yarn guards in textile machines serve for checking the yarn travel, i.e. to determine if the yarn is traveling in an orderly manner or if a break in the yarn has occurred. The known yarn guards are responsive either to break down or collapse of the yarn tension when a yarn break occurs, or to absence of the yarn. Those yarn guards which are responsive to absence of the yarn have a disadvantage in that they react relatively slowly or do not react at all to the yarn break, a consequence thereof being that the yarn slides out of the yarn guard after the yarn breaks. With those yarn guards that respond to the collapse of the yarn tension, it is possible that the yarn will break at a location which is relatively distant from the yarn guard, so that the yarn tension will not vanish im mediately. As a consequence thereof, there will be a time delay before the machine is shut off. Furthermore, with the known yarn guards, the possibility also arises that, for example when operating a doubling winding frame, the broken yarn after a brief stoppage is entrained by the remaining yarns and is wound further without com plete breakdown of the yarn tension. In this case also the yarn guard may not respond reliably to the yarn tension because the time interval for the yarn tension breakdown under the circumstances may consist of only a few milliseconds.

It is accordingly an object of my invention to provide a yarn guard for checking yarn travel in a textile machine which avoids the foregoing disadvantages of the known yarn guards, and more particularly to provide a yarn guard with an extremely high speed of response.

It is furthermore an object of my invention to provide a yarn guard without giving any consideration to its ability to react promptly to the absence of yarn or to collapse of the yarn tension, but rather to provide a yarn guard which is promptly responsive to the state of movement of the yarn, i.e. which determines whether the yarn is traveling or not or if the travel velocity of the yarn has decreased considerably.

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With the foregoing and other objects in view, I provide in accordance with my invention a feeler or sensing member located adjacent the traveling yarn and oscillatable thereby, the sensing member being connected to a transducer adapted to convert mechanical oscillations to electrical oscillations.

My invention makes use of the principle that a moving yarn can cause oscillations in a sensing member located adjacent thereto like for example a violin bow to a violin string. The oscillations of the sensing member that are thus produced can be converted to electrical oscillations with conventional transducers. Transducers that can be employed therefore can be of the electrokinetic type such as microphones based on the transmission of sound through a solid for instance or sound pickup systems based on the principle of the carbon microphone, which are operative capacitively, inductively, magnetostrictively or piezoelectrically. It is, however, also possible to transform the mechanical oscillations of the sensing member into light variations by means of an optical slot diaphragm that is stationary or that is oscillated by the sensing member, and further to transform the light variations with the aid of a light sensitive element into electrical oscillations. It is basically immaterial as to what specific type of transducer is employed in carrying out my invention, however, the transducers most suitable for carrying out the invention are those which yield the greatest output voltage, because such transducers are not very susceptible to interference voltages. Moreover several pickups, for example by means of diode gates, can then operate with a common circuit amplifier without preamplification, so as to detect the yarn break and advantageously shut oil the machine simultaneously,

The type of oscillations produced in the sensing member by the running yarn is per se immaterial. Resonance oscillations as well as other oscillations of the sensing member can be used for the checking process. In some cases it is even possible to cause the sensing member to oscillate solely by the engagement therewith of the individual fibers standing away from the yarn.

Many different expedients are available for achieving extremely short response intervals for the yarn guard, such as employing a sensing member having a very high resonance frequency for example. If this resonance frequency is 5000 c.p.s. or more, for example the oscillation decay periods for a yarn break can be kept very short even without any damping means. For systems with lower resonance frequencies, it can be advantageous to provide auxiliary damping means. It is also possible to obtain a short response interval for the yarn guard when the yarn produces oscillations in the sensing member that are considerably below its resonance frequency. An aperiodic behavior arises therefrom which makes the short shutoff intervals possible.

Other features which are characteristic for the invention are set forth in the appended claims. The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Although the invention is illustrated and described herein as yarn guard for checking yarn travel in a textile machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein, Without departing from the spirit of the invention and within the scope and range of equivalents of the claims. In the figures:

FIGS. 1 and 2 are perspective views of two embodiments of the yarn guard constructed in accordance with my invention;

FIG. 3 is a diagram of an electrical circuit suitable for use with the embodiments of FIGS. 1 and 2; and

FIGS. 3A, 3B and 3C are modified portions of the circuit of FIG. 3.

Referring now to the drawings and first particularly to FIG. 1, there is shown a yarn F which is guided by means of the yarn guide 1 which may have originally been provided with the textile machine (not shown) or by an auxiliary yarn guide which may have subsequently been added to the machine, over a sensing member 2 comprising an oscillatable rod. At the location engaged by the yarn F, the sensing member 2 is provided with an elastically secured layer or tube 3 of sintered corundum or any other suitable component resistant to frictional wear which, due to its great hardness or toughness, prevents abrasion of the sensing member 2. The sensing member 2 is connected to a vibration transducer 4 which in the illustrated embodiment in FIG. 1 consists of a piezoelectrical pickup of the crystalline type such as Rochelle salt, or of the ceramic type such as barium titanate. The piezoelectric crystalline plate 5 is thereby set in oscillation by the sensing member 2. These mechanical oscillations produce electrical voltage oscillations which can be taken off the terminal contacts 6. The piezoelectric crystalline plate 5 is mounted in elastic holders 7 of rubber or elastomer material, for example. In order to achieve the greatest possible damping of the oscillations, the sensing member 2 is also located in an elastic holder 8 of a material similar to that of the holders 7. In order to avoid damage to the system by mechanical impacts or jolts or the like, the free end of the sensing member 2 is provided with a device 9 for limiting the deflections of the sensing member 2, also consisting of elastic material similar to that of the holders 7 and 8. The deflection-limiting device nevertheless does not normally interfere with the oscillations of the sensing member 2 or the tube 3 of sintered corundum that are produced by the traveling yarn F.

FIG. 2 shows an embodiment of a yarn guard that operates in accordance with the same principles as the embodiment of FIG. 1, the elements in FIG. 2 corresponding to Similar elements in FIG. 1 being given the same reference numerals. In the embodiment of FIG. 2, however, the piezoelectric vibration transducer 4 is excited at one of its ends rather than one of its sides as for the embodiment of FIG. 1. Thus an L-shaped member extends from the end of the transducer 4 in the embodiment of FIG. 2 for supporting the sensing member 2.

The electrical oscillations originating in the vibration transducer 4 can be employed for indicating or detecting the yarn break, for shutting off the machine or for releasing automatic control actions by means of a suitable circuit as shown, for example, in FIG. 3. In the circuit of FIG. 3, it is assumed that a warping machine for example, is to be monitored whereby every individual yarn issuing from the warp frame is provided with a yarn guard. The electrical voltage produced by the oscillation transducer is applied at the terminals E and E It is consequently immaterial whether this electrical voltage derives from a piezoelectric pickup 10, as shown in FIG. 3, or an inductive pickup 11, as shown in FIG. 3a, a magnetostrictive pickup, a Hall generator, or a capacitive pickup 12, as shown in FIG. 3b, or a carbon microphone pickup 13, as shown in FIG. 30.

The yarn guard of this invention differs, however, from the known yarn guards such as dropwire for example by a fundamental relationship. With the known yarn guards, something takes place when the yarn breaks, for example, a contact closes mechanically due to the swing of the dropwire. With the yarn guard of the present invention, however, something is caused to stop, namely the oscillations of the sensing member produced by the traveling yarn. In order to stop the winding operation at the breaking of a yarn for example, something must occur however, as in the case of a dropwire. For this reason it is necessary to install a reversing member for the yarn guard constructed in accordance with my invention. This is accomplished as follows:

The resistances 14 and 15 are connected through the terminals 13,, B with the negative and positive poles respectively of a direct voltage source. As long as the yarn travels, the vibration transducers 10-13 respectively, connected to the terminals E E causes a positive voltage to be applied through the diode 16 at the point A to charge the capacitor 20, the appropriate diode of the diode gate being blocked thereby. At a break in the yarn, the voltage applied between the terminals E E collapses abruptly. The negative voltage from the contact terminal B can thereby modulate a circuit amplifier 18, common to all the yarn, through the resistance 14 and the diode 170 so as to energize the electromagnet 19 for example, to turn off the machine. The amplifier 18 is of conventional construction and is connected through the contact terminals C C with an electrical energizing source.

It is evident that only the simple and relatively inexpensive components to the left-hand side of the dot and dash line D in FIG. 3 must be assembled for every individual yarn whereas the relatively more expensive components at the right-hand side of the dot and dash line D, particularly the amplifier 18, can be used for all of the yarns. Special requirements as to quality are not imposed on the vibration transducer that changes the mechanical oscillations to electrical oscillations, since it is unnecessary to have an exact transmission of the vibrating frequency in the case at hand. It is sufficient that the oscillation voltage always exceeds a minimum value for all types of yarn, and the oscillating or alternating voltage can therefore have any value above that minimum value. The limiting value for the lowest voltage is determined by the fact that a positive voltage must be present at the point A during the travel of the yarn and must have a value sufiicient for blocking the associated diode 170.

If a pickup requiring a high ohmic input circuit, for example a piezoelectric pickup 10, is employed as oscillation transducer, it is advantageous to use silicon diodes for the diode gate 17a-17e, particularly when many yarn guards are combined through a common amplifier 18 as in the illustrated embodiment of FIG. 3. The silicon diodes 17a17e then decouple the individual yarn guards so that each yarn guard can furnish a clear switching signal, specifically identifying it, to the amplifier 18 independently of the other yarn guards. Consequently, for example with a warp frame, a determination of the particular yarn that is broken can also be achieved thereby.

Finally it may also be noted that the yarn guard constructed in accordance with my invention is not restricted only to checking yarn movements in the axial or travel direction of the yarn but rather also for checking yarn movements in other directions. It is thus, for example, possible to check the traverse direction of the warn for example at the yarn guide drums of a winding machine.

I claim:

1. Yarn guard for checking yarn travel along a path in a textile machine, comprising sensing means located adjacent the yarn travel path, said sensing means being adapted to oscillate mechanically in response to movement of the yarn past said sensing means and to cease oscillating in response to a break in the yarn, and transducing means connected with said sensing means for converting the mechanical oscillations thereof to electrical oscillations.

2. Yarn guard for checking yarn travel along a path in a textile machine comprising sensing means having a rod slidingly engageable by the traveling yarn and mechanically oscillatable thereby, said rod being disengageable by the yarn upon the occurrence of a break in the yarn whereby said rod ceases to oscillate, and a transducer operatively connected to an end of said rod for converting the mechanical oscillations thereof to electrical e timat ons.

3. Yarn guard according to claim 2 wherein said transducer comprises a piezoelectrical crystalline plate, said rod extending substantially perpendicular to the longitudinal axis of said crystalline plate and being connected by said end to a side of said plate.

4. Yarn guard according to claim 2 wherein said transducer comprises a piezoelectrical crystalline plate, said rod extending substantially perpendicular to the longitudinal axis of said crystalline plate, a substantially L- shaped support member secured by one end thereof to an end of said crystalline plate and by the other end thereof to said end of said rod.

5. Yarn guard according to claim 2 wherein at least the portion of said rod slidingly engageable by the traveling yarn has a layer of material resistant to frictional wear.

6. Yarn guard according to claim 2 wherein the other end of said rod is free, and the yarn guard comprises means for limiting deflections of said mechanically oscillatable rod.

7. For use with a textile machine, a yarn guard for checking yarn travel along a path in the textile machine, said yarn travel path guard comprising sensing means located adjacent the yarn, said sensing means being References Cited UNITED STATES PATENTS 2,506,174 5/1950 Price 2864 2,522,492 9/ 1950 Anderson 58-130 X 3,140,604 7/1964 Bernet 2864 X 3,153,312 10/1964 Bushey 22611 X 3,188,192 6/1965 Parobeck et al 226-11 X FOREIGN PATENTS 1,141,212 12/1962 Germany.

ALLEN N. KNOWLES, Primary Examiner.

M. HENSON WOOD, .TR., Examiner.

I N. ERLICH, Assistant Examiner. 

